Our previous findings suggest that developmental alternations in hormone binding mechanisms in steroid responsive tissues of the rat might play an important role in determining the neuroendocrine and tissue responses of the adult of circulating steroid hormones. For this reason, we will continue our examination of the influence of sexual differentiation on the interaction of estradiol with steroid responsive mechanisms in tissues of the hypothalamo-pituitary-gonadal axis of males, females, and neonatally androgenized adult female rats. Using both in vitro and in vivo techniques, we will compare macromolecular receptors for estrogen, intracellular transport of estrogen, estrogen induced specific protein synthesis, and physiological responses to estrogen. These studies will be performed in an attempt to determine (1) How the hormonal environment during development alters the potentiality of estrogen responsive mechanisms in the adult, and (2) How estrogen sensitive mechanisms in the adult respond to changes in the hormonal environment. By applying recently developed techniques for studying macromolecular receptors, intracellular transport, and metabolic systems to the examination of males, females, and neonatally androgenized females, we should be able to contribute markedly to the understanding of the developmental alterations in the mechanisms involved in the recognition of and response to steroid hormones.